Battery pecentage jumps around
Phone shows that's its charging but won't turn on.
Battery expanded and warped your screen or back cover. If this happens act fast because this is called out gassing which can create other issues within your device. * Please do not attempt to "pop" or take out the battery on your own as this can be very dangerous.
Phone gets hot with the battery symbol on.
Phone turns off but the battery still has charge.
iPhone users* check settings-battery and look at your battery health. There will be insights, suggestions and whether or not your battery needs to be serviced. Support.apple.com
If its been more than 1 year or you've had 300-500 charge cycles
According to the manufacturer, lithium ion batteries have about a 300-500 charge cycle---
meaning that everytime you plug that device into a wall or car charger that's is one charge cycle. After 1000 charge cycle, the batteries capacity decreases significantly.
****For tips on how to preserve your lithium ion battery's 🔋 life visit support.google.com OR
www.tek.com for lithium ion battery maintenance guidelines.